WO2013114467A1

WO2013114467A1 - Power storage system

Info

Publication number: WO2013114467A1
Application number: PCT/JP2012/000749
Authority: WO
Inventors: 高橋　賢司; 勇二西; 裕之海谷
Original assignee: トヨタ自動車株式会社
Priority date: 2012-02-03
Filing date: 2012-02-03
Publication date: 2013-08-08

Abstract

[Problem] In a power storage device with multiple power storage components connected in parallel, the activation of a current blocking device in a power storage component causes changes in the current flowing in a power storage component in which the current blocking device is not activated. [Solution] This power storage system includes: a power storage device that includes parallelly connected multiple power storage components; and a controller for controlling charging/discharging of the power storage device. Each power storage component has a current blocking device for interrupting a current path inside the power storage component. The controller controls charging/discharging of the power storage device with reference to the values of currents that flow in power storage components with uninterrupted current paths. The values of the currents flowing in the power storage components with uninterrupted current paths change according to an increase in the number of current blocking devices that are in an open state.

Description

Power storage system

The present invention relates to a power storage system that controls charging / discharging of a power storage device including a plurality of power storage elements each having a current breaker.

In the assembled battery described in Patent Document 1, in a configuration in which a plurality of batteries are connected in parallel, a fuse is connected to each single cell connected in parallel. The fuse cuts off the current path by fusing when an excessive current flows.

JP 05-275116 A JP 2011-135657 A JP 2008-182779 A

In the configuration in which a fuse is connected to each battery connected in parallel, the value of the current flowing through each battery connected in parallel changes as the number of blown fuses increases. When the current value changes, it is necessary to protect the battery according to the current value.

The power storage system according to the present invention includes a power storage device including a plurality of power storage elements connected in parallel, and a controller that controls charging / discharging of the power storage device. Each power storage element has a current breaker that blocks a current path inside the power storage element. The controller controls charging / discharging of the power storage device with reference to a current value flowing through the power storage element whose current path is not interrupted. The value of the current flowing through the power storage element whose current path is not interrupted changes as the number of current breakers in the interrupted state increases.

In a power storage device in which a plurality of power storage elements are connected in parallel, the value of a current flowing through a power storage element whose current path is not interrupted changes as the number of current breakers in the interrupted state increases. When the value of the current flowing through the power storage element changes, charging / discharging of the power storage device is preferably controlled based on this current value. Thereby, an electrical storage element can be protected by charge / discharge control of an electrical storage apparatus.

The power storage device can be composed of a plurality of power storage blocks connected in series. Here, each power storage block can be composed of a plurality of power storage elements connected in parallel. In the power storage device having such a configuration, as the number of current breakers in the cut-off state, the largest number among the number of current breakers in the cut-off state in each power storage block can be used. Thereby, all the electrical storage elements can be protected in charge / discharge control of the electrical storage device.

A power storage device can be configured by connecting another power storage element in series to each power storage element connected in parallel. In other words, it is possible to prepare a plurality of power storage blocks in which a plurality of power storage elements are connected in series, and to connect these power storage blocks in parallel.

The controller can reduce the value of the current flowing through the power storage device as the number of current breakers in the breaking state increases. Since the plurality of power storage elements included in the power storage device are connected in parallel, when the value of the current flowing through the power storage device is constant, the current path is cut off when the number of current breakers in the cut-off state increases. The value of the current flowing through the non-storage element increases.

Therefore, by reducing the current value flowing through the power storage device, it is possible to suppress an increase in the current value flowing through the power storage element whose current path is not interrupted. By suppressing an increase in the value of the current flowing through the power storage element, it is possible to suppress the deterioration of the power storage element and to prevent the current breaker from being easily activated.

When controlling the charge / discharge of the power storage device, the charge / discharge of the power storage device can be limited as the estimated temperature inside the power storage element approaches the upper limit temperature. By limiting charging / discharging of the power storage device, it is possible to suppress the internal temperature of the power storage element from becoming higher than the upper limit temperature.

The temperature inside the electricity storage element can be estimated using a temperature change amount based on a reference current value. For example, the temperature inside the electricity storage element can be estimated based on the temperature on the surface of the electricity storage element and the temperature change amount based on the current value. Here, as the number of current breakers in the cut-off state increases, the value of the current flowing through the storage element whose current path is not interrupted changes. Therefore, when calculating the internal resistance of the storage element, It is necessary to use a current value. Thereby, the precision at the time of estimating the internal temperature of an electrical storage element can be improved.

The controller can not permit charging / discharging of the power storage device when the number of current breakers in the breaking state is equal to or greater than the first threshold. If the number of current breakers in the cut-off state increases too much, it becomes difficult to ensure the input / output performance of the power storage device. Therefore, when the number of current breakers in the cut-off state is equal to or greater than the first threshold value, charging / discharging of the power storage device is performed in a state where it is difficult to secure input / output performance of the power storage device by not permitting charge / discharge of the power storage device Can be prevented. For example, when the power storage device is mounted on a vehicle and the vehicle is driven using the output of the power storage device, the controller can not drive the vehicle.

The controller can issue a warning when the number of current breakers in the interrupted state is equal to or greater than a second threshold value that is less than the first threshold value and less than the first threshold value. Thereby, before the number of current breakers in the cut-off state reaches the first threshold value, the user or the like can confirm the abnormality of the power storage device by the warning. Then, the power storage element or the power storage device can be replaced before the power storage device is no longer charged or discharged.

As the current breaker, a fuse, a PTC element, or a current cutoff valve can be used. The fuse interrupts the current path by fusing. The PTC element cuts off the current path due to an increase in resistance accompanying a temperature rise. The current cutoff valve is deformed in response to an increase in the internal pressure of the power storage element and cuts off the current path.

It is a figure which shows the structure of a battery system. It is a figure which shows the structure of an assembled battery. It is a figure which shows the structure of a cell. It is a figure which shows the structure of the assembled battery which is a modification. In Example 1, it is a flowchart which shows the process which controls charging / discharging of an assembled battery. It is a figure which shows the relationship between the time-dependent change of the internal resistance accompanying the abrasion deterioration of a battery block, and the internal resistance accompanying the action | operation of a current circuit breaker. It is a figure which shows the relationship between the electric current command value at the time of charging / discharging, and interruption | blocking number. It is a figure which shows the characteristic of a current breaker. In Example 3, it is a flowchart which shows the process which controls charging / discharging of an assembled battery. In Example 3, it is a figure which shows the relationship between the output performance of an assembled battery, and the number of interruption | blocking. In the modification of Example 3, it is a flowchart which shows the process which controls charging / discharging of an assembled battery.

Hereinafter, examples of the present invention will be described.

A battery system (corresponding to a power storage system) that is Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of a battery system. The battery system of this embodiment is mounted on a vehicle.

Vehicles include hybrid cars and electric cars. The hybrid vehicle includes an engine or a fuel cell as a power source for running the vehicle in addition to the assembled battery described later. The electric vehicle includes only an assembled battery described later as a power source for running the vehicle.

A system main relay SMR-B is provided on the positive electrode line PL connected to the positive electrode terminal of the assembled battery (corresponding to a power storage device) 10. System main relay SMR-B is switched between on and off by receiving a control signal from controller 40. A system main relay SMR-G is provided on the negative electrode line NL connected to the negative electrode terminal of the assembled battery 10. System main relay SMR-G is switched between on and off by receiving a control signal from controller 40.

System main relay SMR-P and current limiting resistor R are connected in parallel to system main relay SMR-G. System main relay SMR-P and current limiting resistor R are connected in series. System main relay SMR-P is switched between on and off by receiving a control signal from controller 40. The current limiting resistor R is used to suppress an inrush current from flowing when the assembled battery 10 is connected to a load (specifically, a booster circuit 32 described later).

When connecting the assembled battery 10 to a load, the controller 40 switches the system main relays SMR-B and SMR-P from off to on. As a result, a current can flow through the current limiting resistor R, and an inrush current can be suppressed.

Next, after switching the system main relay SMR-G from off to on, the controller 40 switches the system main relay SMR-P from on to off. Thereby, connection of the assembled battery 10 and load is completed, and the battery system shown in FIG. 1 will be in a starting state (Ready-On). On the other hand, when cutting off the connection between the assembled battery 10 and the load, the controller 40 switches the system main relays SMR-B and SMR-G from on to off. Thereby, the operation of the battery system shown in FIG. 1 is stopped.

The booster circuit 32 boosts the output voltage of the assembled battery 10 and outputs the boosted power to the inverter 33. Further, the booster circuit 32 can step down the output voltage of the inverter 33 and output the lowered power to the assembled battery 10. The booster circuit 32 operates in response to a control signal from the controller 40. In the battery system of this embodiment, the booster circuit 32 is used, but the booster circuit 32 may be omitted.

The inverter 33 converts the DC power output from the booster circuit 32 into AC power, and outputs the AC power to the motor / generator 34. The inverter 33 converts AC power generated by the motor / generator 34 into DC power and outputs the DC power to the booster circuit 32. As the motor generator 34, for example, a three-phase AC motor can be used.

The motor / generator 34 receives AC power from the inverter 33 and generates kinetic energy for running the vehicle. When the vehicle is driven using the output power of the assembled battery 10, the kinetic energy generated by the motor / generator 34 is transmitted to the wheels.

When the vehicle is decelerated or stopped, the motor / generator 34 converts kinetic energy generated during braking of the vehicle into electric energy (AC power). The inverter 33 converts AC power generated by the motor / generator 34 into DC power and outputs the DC power to the booster circuit 32. The booster circuit 32 outputs the electric power from the inverter 33 to the assembled battery 10. Thereby, regenerative electric power can be stored in the assembled battery 10.

FIG. 2 shows the configuration of the assembled battery 10. The assembled battery 10 has a plurality of battery blocks (corresponding to power storage blocks) 11 connected in series. By connecting a plurality of battery blocks 11 in series, the output voltage of the assembled battery 10 can be secured. Here, the number of battery blocks 11 can be appropriately set in consideration of the voltage required for the assembled battery 10.

Each battery block 11 has a plurality of single cells (corresponding to power storage elements) 12 connected in parallel. By connecting a plurality of single cells 12 in parallel, the capacity [Ah] of the battery block 11 (the assembled battery 10) can be increased, and the distance when the vehicle is driven using the output of the assembled battery 10 is increased. Can do. The number of single cells 12 constituting each battery block 11 can be appropriately set in consideration of the capacity required for the assembled battery 10.

Since the plurality of battery blocks 11 are connected in series, an equal current flows through each battery block 11. In each battery block 11, a plurality of unit cells 12 are connected in parallel, so that the current value flowing through each unit cell 12 is the current value flowing through the battery block 11 by the number of unit cells 12 constituting the battery block 11. The current value is divided by (total). Specifically, when the total number of the single cells 12 constituting the battery block 11 is N and the current value flowing through the battery block 11 is Is, the current value flowing through the single cell 12 is Is / N. Here, it is assumed that there is no variation in resistance among the plurality of single cells 12 constituting the battery block 11.

As the single battery 12, a secondary battery such as a nickel metal hydride battery or a lithium ion battery can be used. An electric double layer capacitor (capacitor) can be used instead of the secondary battery. For example, as the single battery 12, a 18650 type battery can be used. The 18650 type battery is a so-called cylindrical battery, which has a diameter of 18 [mm] and a length of 65.0 [mm]. In a cylindrical battery, a battery case is formed in a cylindrical shape, and a power generation element for charging and discharging is accommodated in the battery case. The configuration of the power generation element will be described later.

The cell 12 includes a power generation element 12a and a current breaker 12b as shown in FIG. The power generation element 12 a and the current breaker 12 b are accommodated in a battery case that constitutes the exterior of the unit cell 12. The power generation element 12a is an element that performs charging and discharging, and includes a positive electrode plate, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate. The positive electrode plate includes a current collector plate and a positive electrode active material layer formed on the surface of the current collector plate. The negative electrode plate has a current collector plate and a negative electrode active material layer formed on the surface of the current collector plate. The positive electrode active material layer includes a positive electrode active material and a conductive agent, and the negative electrode active material layer includes a negative electrode active material and a conductive agent.

When a lithium ion secondary battery is used as the single battery 12, for example, the current collector plate of the positive electrode plate can be made of aluminum, and the current collector plate of the negative electrode plate can be made of copper. As the positive electrode active material, for example, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ can be used, and as the negative electrode active material, for example, carbon can be used. An electrolyte solution is infiltrated into the separator, the positive electrode active material layer, and the negative electrode active material layer. Instead of using the electrolytic solution, a solid electrolyte layer may be disposed between the positive electrode plate and the negative electrode plate.

The current breaker 12b is used to cut off the current path inside the unit cell 12. That is, when the current breaker 12b operates, the current path inside the unit cell 12 is cut off. As the current breaker 12b, for example, a fuse, a PTC (Positive Temperature Coefficient) element, or a current cut-off valve can be used. These current breakers 12b can be used individually or in combination.

The fuse as the current breaker 12b is blown according to the current flowing through the fuse. By blowing the fuse, the current path inside the unit cell 12 can be mechanically interrupted. Thereby, it can prevent that an excessive electric current flows into the electric power generation element 12a, and can protect the cell 12 (electric power generation element 12a). The fuse as the current breaker 12b can be accommodated in the battery case or can be provided outside the battery case. Even when a fuse is provided outside the battery case, the fuse is provided in each unit cell 12 and connected in series with each unit cell 12.

The PTC element as the current breaker 12b is arranged in the current path of the unit cell 12, and increases the resistance according to the temperature rise of the PTC element. When the current flowing through the PTC element increases, the temperature of the PTC element rises due to Joule heat. As the resistance of the PTC element increases as the temperature of the PTC element rises, current can be cut off in the PTC element. Thereby, it can prevent that an excessive electric current flows into the electric power generation element 12a, and can protect the cell 12 (electric power generation element 12a).

The current cut-off valve as the current breaker 12b is deformed in accordance with the increase in the internal pressure of the unit cell 12, and can cut off the current path inside the unit cell 12 by breaking the mechanical connection with the power generation element 12a. it can. The inside of the unit cell 12 is in a sealed state, and when gas is generated from the power generation element 12a due to overcharging or the like, the internal pressure of the unit cell 12 increases. When gas is generated from the power generation element 12a, the unit cell 12 (power generation element 12a) is in an abnormal state. The mechanical connection with the power generation element 12a can be broken by deforming the current cutoff valve in response to the increase in the internal pressure of the unit cell 12. Thereby, it can block | prevent that charging / discharging electric current flows into the electric power generation element 12a in an abnormal state, and can protect the cell 12 (electric power generation element 12a).

The monitoring unit 20 shown in FIG. 1 detects the voltage of each battery block 11 and outputs the detection result to the controller 40. The current sensor 31 detects the value of the current flowing through the assembled battery 10 and outputs the detection result to the controller 40. For example, when the assembled battery 10 is being discharged, a positive value can be used as the current value detected by the current sensor 31. Further, when the battery pack 10 is being charged, a negative value can be used as the current value detected by the current sensor 31. The current sensor 31 may be provided not on the positive line PL but on the negative line NL as long as it can detect the value of the current flowing through the assembled battery 10. A plurality of current sensors 31 can also be used. Here, in consideration of cost and physique, it is desirable to provide one current sensor 31 for one assembled battery 10 as in the present embodiment.

The controller 40 has a built-in memory 41, and the memory 41 stores a program for operating the controller 40 and specific information. The memory 41 can also be provided outside the controller 40.

The assembled battery 10 of the present embodiment has the configuration shown in FIG. 2, but is not limited thereto. Specifically, the assembled battery 10 may be configured as shown in FIG. In FIG. 4, a plurality of battery blocks (corresponding to power storage blocks) 11 are connected in parallel. The number of battery blocks 11 can be appropriately determined based on the capacity required for the assembled battery 10. Each battery block 11 has a plurality of single cells 12 connected in series. In the plurality of battery blocks 11, the number of unit cells 12 constituting each battery block 11 is the same. The number of unit cells 12 constituting the battery block 11 can be appropriately determined based on the voltage required for the assembled battery 10 and the like.

Next, a part of processing in the battery system of the present embodiment will be described with reference to the flowchart shown in FIG. The process shown in FIG. 5 is executed by the controller 40.

In step S101, the controller 40 confirms the operating state of the current breaker 12b in each battery block 11.

For example, the internal resistance of each battery block 11 can be calculated, and the operating state of the current breaker 12b can be confirmed based on the calculated internal resistance. A plurality of relations between current values and voltage values in each battery block 11 are acquired, and the internal resistance of each battery block 11 is determined from the slope of the approximate straight line when these acquired values are plotted in the current and voltage coordinate system. Can be calculated.

In the battery block 11, since the plurality of single cells 12 are connected in parallel, when the current breaker 12b is activated, the internal resistance of the battery block 11 including the current breaker 12b in the activated state is increased. That is, when the current breaker 12b is activated, the current path in the battery block 11 is reduced, and the internal resistance of the battery block 11 is increased.

Here, when the internal resistance of each battery block 11 is equal, the internal resistance of the battery block 11 including the current circuit breaker 12b in the operating state is greater than the internal resistance of the battery block 11 in which all the current circuit breakers 12b are not operating. Also gets higher.

Therefore, by detecting an increase in the internal resistance of the battery block 11, the operating state of the current breaker 12b can be confirmed. Since the internal resistance of the battery block 11 increases as the number of the current breakers 12b in the operating state increases, the number of current breakers 12b in the operating state can be specified according to the increase amount of the internal resistance. . A method (one example) for specifying the number of current breakers 12b in the operating state will be described below.

The internal resistance of the battery block 11 is acquired at each of the different times t1 and t2, and the resistance change rate is calculated. The resistance change rate can be calculated based on the following formula (1).

Rr = R2 / R1 (1)

In the formula (1), Rr represents a resistance change rate. R1 indicates the internal resistance of the battery block 11 acquired at time t1, and R2 indicates the internal resistance of the battery block 11 acquired at time t2. The time t2 can be the current timing when the internal resistance of the battery block 11 is acquired. The time t1 can be the previous timing when the internal resistance of the battery block 11 is acquired. That is, time t1 is a timing before time t2.

Next, it is determined whether or not the interval between times t1 and t2 is within a predetermined period T. The predetermined period T can be determined based on the speed at which the deterioration of the battery block 11 proceeds. Hereinafter, a method for determining the predetermined period T will be described.

The change in internal resistance when the battery block 11 (single cell 12) deteriorates can be acquired in advance by experiments. As the deterioration of the battery block 11, deterioration due to wear can be considered. The wear deterioration is deterioration caused by wear of members (particularly the power generation element 12a) constituting the battery block 11 (unit cell 12).

By conducting an experiment in which the battery block 11 is repeatedly charged / discharged in a predetermined manner, the change in internal resistance with time can be acquired in advance. The change in internal resistance with time can be obtained as a curve C1 shown in FIG. As shown in FIG. 6, the internal resistance of the battery block 11 increases as time passes, in other words, as the wear deterioration of the battery block 11 progresses.

If the curve C1 shown in FIG. 6 is used, the period when the internal resistance increases by a predetermined amount with respect to the internal resistance at time t1 due to wear deterioration of the battery block 11 can be specified in advance. In a period shorter than this period, when the internal resistance at time t2 is increased by a predetermined amount with respect to the internal resistance at time t1, the battery block 11 has not only increased internal resistance due to wear deterioration but also current. It can be determined that an increase in internal resistance due to the operation of the circuit breaker 12b has occurred.

In the wear deterioration, the internal resistance of the battery block 11 gradually increases, whereas when the current breaker 12b is activated, the internal resistance of the battery block 11 rapidly increases. Therefore, when the internal resistance of the battery block 11 increases by a predetermined amount in a period sufficiently shorter than the period until the internal resistance of the battery block 11 increases by a predetermined amount due to wear deterioration, the current breaker 12b is activated. Can be determined. By monitoring this time interval, it can be determined whether or not the current breaker 12b is operating.

For example, when only wear deterioration has progressed, it is assumed that the internal resistance of the battery block 11 becomes 1.1 times when half a year has elapsed from time t1 based on the curve C1 shown in FIG. Here, when the internal resistance of the battery block 11 becomes 1.1 times between the time t1 and the time t2 even though the interval between the time t1 and the time t2 shown in FIG. 6 is within one month, It can be determined that the current breaker 12b is operating.

The above-described predetermined period T is a period when the resistance change rate acquired by the above-described processing is generated only by wear deterioration. Specifically, the predetermined period T is a period from the time t1 to the time t2 until the rate of increase in internal resistance (resistance change rate) occurs, and is a period specified from the curve C1 shown in FIG. It is.

When the interval between the times t1 and t2 is longer than the predetermined period T, it can be determined in the battery block 11 that the current breaker 12b is not operating. On the other hand, when the interval between the times t1 and t2 is within the predetermined period T, it can be determined that the current breaker 12b is operating in the battery block 11.

Based on the resistance change rate Rr, the number of current breakers 12b in the operating state (referred to as the number of breaks) can be specified. If the internal resistance of the battery block 11 before the operation of the current breaker 12b is Ra and the internal resistance of the battery block 11 after the operation of the current breaker 12b is Rb, the internal resistances Ra and Rb are expressed by the following formula (2 ).

Rb = Ra × N / (N−m) (2)

In the formula (2), N indicates the number of unit cells 12 constituting each battery block 11, in other words, the number of unit cells 12 connected in parallel. m indicates the total number (the number of interruptions) of the current breakers 12b in the operating state in each battery block 11. Since the current breaker 12b is provided in each unit cell 12, the number of breaks m is the total number of the unit cells 12 having the current breaker 12b in the operating state. In the battery block 11, when all the current breakers 12b are not operating, the breaking number m is zero.

When the current breaker 12b is activated, the internal resistance of the battery block 11 is increased according to the number of current breakers 12b in the activated state. That is, as shown in Expression (2), the internal resistance Rb of the battery block 11 after the current breaker 12b is activated is N with respect to the internal resistance Ra of the battery block 11 before the current breaker 12b is activated. / (Nm) times. Since the value of “N / (N−m)” is a value larger than 1, the internal resistance Rb is higher than the internal resistance Ra.

If equation (2) is transformed, it can be expressed by equation (3).

Rb / Ra = N / (Nm) (3)

The value of “Rb / Ra” shown in Equation (3) corresponds to the value of “Rr (= R1 / R2”) shown in Equation (1). That is, the resistance change rate Rr becomes equal to the value of “N / (N−m)”. Therefore, based on the resistance change rate Rr and the number (predetermined value) N, the cutoff number m can be calculated.

In the above description, the interruption number m is calculated based on the internal resistance of the battery block 11, but the interruption number m can also be calculated based on the full charge capacity of the battery block 11. That is, when the current breaker 12b is activated, the full charge capacity of the battery block 11 including the current breaker 12b in the activated state decreases. Specifically, the full charge capacity of the battery block 11 after the current breaker 12b is activated is (N−m) / N with respect to the full charge capacity of the battery block 11 before the current breaker 12b is activated. Doubled. Based on this relationship, the cutoff number m can be calculated.

On the other hand, when the assembled battery 10 has the configuration shown in FIG. 4, for example, by detecting the current or voltage of each battery block 11, the operating state of the current breaker 12 b can be confirmed. In the configuration shown in FIG. 4, when the current breaker 12b is activated, no current flows through the battery block 11 including the current breaker 12b in the activated state. Therefore, by confirming this state, the operating state of the current breaker 12b can be confirmed.

In step S102, the controller 40 detects whether or not the current breaker 12b is operating in each battery block 11 based on the confirmation result in step S101. In any battery block 11, when the current breaker 12b is operating, the process proceeds to step S103. In all battery blocks 11, when the current breaker 12b is not operating, the process shown in FIG.

In step S103, the controller 40 specifies the number of current breakers 12b in operation (the number of interruptions) in each battery block 11, and specifies the largest interruption number m_max among the interruption numbers in all the battery blocks 11. To do. When all of the single cells 12 constituting the battery block 11 are operating with the current breaker 12b, the number of breaks in the battery block 11 is the total number N of the single cells 12 constituting the battery block 11. Moreover, in all the single cells 12 constituting the battery block 11, when the current breaker 12b is not operating, the number of breaks is “0”. The number of interrupts varies between 0 and N.

When the assembled battery 10 shown in FIG. 4 is used, the interruption number m_max is the number of battery blocks 11 including the current breaker 12b in the operating state. In the assembled battery 10 shown in FIG. 4, when the current breaker 12 b included in one battery block 11 is activated, no current flows through the battery block 11. In the configuration shown in FIG. 4, if at least one current breaker 12 b included in the battery block 11 is activated, no current flows through the battery block 11. Therefore, when specifying the number of interruptions m_max, it is only necessary to specify the number of battery blocks 11 in which no current flows due to the operation of the current breaker 12b.

In step S104, the controller 40 determines a current command value for controlling charging / discharging of the assembled battery 10. Specifically, the controller 40 decreases the charge / discharge current of the assembled battery 10 in response to an increase in the number of interruptions m_max as the current command value. When the current command value is set to Ia before performing the process shown in FIG. 5, the controller 40 sets the current command value to Ib based on the following equation (4).

Ib = Ia × (N−m_max) / N (4)

In Equation (4), N is the total number of unit cells 12 constituting each battery block 11, and m_max is the maximum number of current breakers 12b in the operating state. As can be seen from the equation (4), since the value of “(N−m_max) / N” is a value smaller than 1, the current command value Ib is smaller than the current command value Ia.

On the other hand, in the configuration shown in FIG. 4, N shown in Equation (4) is the number of battery blocks 11 connected in parallel, and m_max is the number of battery blocks 11 including the current breaker 12b in the operating state. is there. In all the battery blocks 11, when the current breaker 12b is not operating, the breaking number m_max is “0”. In all the battery blocks 11, when the current breaker 12b is operating, the breaking number m_max is “N”. In all the battery blocks 11, when the current breaker 12b is operating, it becomes impossible to pass a current through the assembled battery 10. The blocking number m_max varies between “0” and “N”.

In step S105, the controller 40 controls charging / discharging of the assembled battery 10 based on the current command value Ib set in step S104. Specifically, based on the current command value Ib, the controller 40 reduces the upper limit power that allows the battery pack 10 to be charged, or reduces the upper limit power that allows the battery pack 10 to be discharged. When lowering the upper limit power, the upper limit power before being lowered can be multiplied by a value of “(N−m_max) / N”. By reducing the upper limit power that allows charging / discharging of the assembled battery 10, the value of the current flowing through the assembled battery 10 can be limited.

In the configuration shown in FIG. 2 or FIG. 4, when the interruption number m_max is “N”, the current cannot flow through the assembled battery 10, so the controller 40 does not charge / discharge the assembled battery 10. Specifically, the controller 40 can set the upper limit power that allows charging and discharging of the assembled battery 10 to 0 [kW]. In addition, when the interruption number m_max approaches “N”, charging / discharging of the assembled battery 10 may not be performed. The value of the cutoff number m_max when charging / discharging of the assembled battery 10 is not performed can be set as appropriate based on the viewpoint of ensuring traveling of the vehicle.

When the vehicle is running, the controller 40 can limit the current during charging / discharging of the battery pack 10 by controlling the operation of the inverter 33, for example. On the other hand, when the power of the external power source is supplied to the assembled battery 10 using the charger, the controller 40 controls the operation of the charger to charge the assembled battery 10 based on the current command value Ib. The current can be limited. The external power source is a power source provided outside the vehicle, and an example of the external power source is a commercial power source.

When the external power supply supplies AC power, the charger converts AC power into DC power and supplies DC power to the assembled battery 10. The charger can be mounted on the vehicle or can be provided outside the vehicle separately from the vehicle. When supplying power from the external power source to the assembled battery 10, the charger can convert the voltage value.

As means for supplying power to the assembled battery 10 from an external power source, there are means using wired or wireless. As a means using a wire, a connector (so-called plug) connected to an external power source is connected to a connector (so-called inlet) provided in the vehicle, thereby supplying power from the external power source to the assembled battery 10. Can do. Further, as a means using radio, electric power from an external power source can be supplied to the assembled battery 10 using electromagnetic induction or a resonance phenomenon.

On the other hand, when the electric power of the assembled battery 10 is supplied to an external device using the power supply device, the controller 40 controls the operation of the power supply device, thereby controlling the discharge current of the assembled battery 10 based on the current command value Ib. Can be limited. When supplying the power of the assembled battery 10 to an external device, the power supply apparatus can convert the DC power from the assembled battery 10 into AC power and supply the AC power to the external device. Here, the power feeding device can convert the voltage value.

The external device is an electronic device arranged outside the vehicle and is operated by receiving electric power from the assembled battery 10. For example, by connecting a connector connected to an external device to a connector connected to the assembled battery 10, power can be supplied from the assembled battery 10 to the external device. An example of the external device is a home appliance.

FIG. 7 shows the relationship between the current command value and the number of interruptions m_max. In FIG. 7, the vertical axis represents the current command value, and the horizontal axis represents the number of interruptions m_max. With respect to the vertical axis in FIG. 7, a positive value is a current command value when discharging the assembled battery 10, and a negative value is a current command value when charging the assembled battery 10. With respect to the horizontal axis in FIG. 7, the blockage number m_max increases as it moves to the right. As shown in FIG. 7, the current command value at the time of charge / discharge decreases as the number of interruptions m_max increases.

In the battery block 11 shown in FIG. 2, when the current breaker 12b is activated, no current flows through the unit cell 12 having the current breaker 12b in the activated state. Moreover, the current which is going to flow through the single cell 12 which has the current circuit breaker 12b in an operation state flows into the other single cell 12 connected in parallel with the single cell 12 which has the current circuit breaker 12b in the operation state. End up. Here, when the current value Ia flowing through the assembled battery 10 (battery block 11) is not limited, the current value flowing through the other unit cells 12 is Ia / (N−m_max). Since the value of “N−m_max” is smaller than the value of “N”, the value of the current flowing through the other unit cells 12 increases.

When the value of the current flowing through the unit cell 12 increases, in other words, when the current load on the unit cell 12 increases, deterioration due to uneven concentration of salt in the electrolyte of the unit cell 12 (called high-rate degradation) occurs. There is a risk that. High-rate deterioration is likely to occur when charging or discharging is performed at a high rate. Further, when a lithium ion secondary battery is used as the single battery 12, lithium may be deposited.

Furthermore, when the value of the current flowing through the unit cell 12 increases, the current breaker 12b is likely to operate. FIG. 8 shows general characteristics of the current breaker 12b. In FIG. 8, the vertical axis represents the energization time of the current breaker 12b, and the horizontal axis represents the current value flowing through the current breaker 12b. A boundary line (one example) shown in FIG. 8 indicates a boundary between a region where the current breaker 12b operates and a region where the current breaker 12b does not operate. The region above the boundary line shown in FIG. 8 is a region where the current breaker 12b operates. As shown in FIG. 8, when the current value increases, the current breaker 12b is likely to operate in a short time.

According to the present embodiment, since the current value flowing through the assembled battery 10 is limited according to the number of the current breakers 12b in the operating state, the current load on the unit cell 12 can be reduced. Specifically, as the number of the current breakers 12b in the operating state increases, the value of the current flowing through the battery pack 10 is reduced, so that the unit cell 12 in which the current breaker 12b is not activated is excessive. It is possible to prevent the current from flowing and protect the unit cell 12. Moreover, the electric current value which flows into the electric current breaker 12b which is not act | operating can also be restrict | limited, and it can suppress that the electric current breaker 12b becomes easy to operate | move.

In the present embodiment, since the current value flowing through the assembled battery 10 is limited based on the cutoff number m_max as the maximum value, even in the battery block 11 having the largest number of current breakers 12b in the operating state, The current load on the battery 12 can be reduced. That is, all the unit cells 12 constituting the assembled battery 10 can be protected. In addition, since the current value of the assembled battery 10 is limited according to the number of interruptions m_max, it is possible to prevent the charging / discharging of the assembled battery 10 from being restricted more than necessary, and within a range where all the unit cells 12 can be protected. Therefore, the assembled battery 10 can be used efficiently.

Even in the configuration shown in FIG. 4, in any battery block 11, even if the current breaker 12 b is activated, an excessive current flows to the battery block 11 in which the current breaker 12 b is not activated. Can be suppressed. Moreover, the electric current value which flows into the electric current breaker 12b which is not act | operating can also be restrict | limited, and it can suppress that the electric current breaker 12b becomes easy to operate | move.

A battery system that is Embodiment 2 of the present invention will be described. About the member which has the same function as the member demonstrated in Example 1, detailed description is abbreviate | omitted using the same code | symbol. Hereinafter, differences from the first embodiment will be mainly described.

In this embodiment, the temperature (internal temperature) inside the battery block 11 (unit cell 12) is estimated, and charging / discharging of the assembled battery 10 is controlled so that the internal temperature does not become higher than the upper limit temperature. The internal temperature of the battery block 11 (cell 12) is obtained by adding the temperature rise due to the internal resistance of the cell 12 to the temperature (surface temperature) on the surface of the battery block 11 (cell 12). Can be estimated.

If the temperature sensor is arranged on the surface of the battery block 11 (unit cell 12), the controller 40 can acquire the surface temperature of the battery block 11 (unit cell 12) from the output of the temperature sensor. When the temperature sensor is arranged at a position away from the surface of the battery block 11 (unit cell 12), the controller 40 detects the temperature detected by the temperature sensor and the temperature sensor and the battery block 11 (unit cell 12). Thus, the surface temperature of the battery block 11 (unit cell 12) can be estimated.

Here, if the temperature detected by the temperature sensor and the surface temperature of the battery block 11 (unit cell 12) are associated in advance, the surface temperature of the battery block 11 (unit cell 12) is determined from the temperature detected by the temperature sensor. Can be identified (estimated). Data indicating the correspondence between the temperature detected by the temperature sensor and the surface temperature of the battery block 11 (unit cell 12) can be stored in the memory 41 in advance.

Generally, charging / discharging of the assembled battery 10 is controlled so that the surface temperature of the battery block 11 (unit cell 12) does not exceed a preset upper limit temperature. The upper limit temperature is a preset temperature based on the viewpoint of suppressing the generation of gas from the unit cell 12 (power generation element 12a) when the unit cell 12 is in a high temperature state.

Here, the unit cell 12 generates heat by charging and discharging, and the internal temperature of the unit cell 12 tends to be higher than the surface temperature of the unit cell 12. Therefore, in order to suppress the generation of gas, it is preferable to control charging / discharging of the unit cell 12 based on the internal temperature of the unit cell 12.

When estimating the internal temperature of the cell 12, it is necessary to consider the temperature rise caused by the internal resistance of the cell 12. That is, when estimating the internal temperature of the cell 12, it is necessary to consider the heat generated by the current flowing through the cell 12. Thus, the internal temperature of the unit cell 12 depends on the value of the current flowing through the unit cell 12. Here, the amount of heat generated inside the unit cell 12 is a value obtained by multiplying the value obtained by squaring the current value of the unit cell 12 by the internal resistance of the unit cell 12.

The internal temperature of the single cell 12 can be estimated based on the temperature outside the single cell 12 (temperature that can be acquired by the temperature sensor) and the amount of temperature increase corresponding to the heat generated by the current flowing through the single cell 12. . The temperature outside the unit cell 12 may be a temperature on the surface of the unit cell 12 or a temperature at a position away from the surface of the unit cell 12.

When the temperature on the surface of the unit cell 12 is acquired, the internal temperature of the unit cell 12 can be estimated in consideration of the heat conduction inside the unit cell 12. When the temperature at a position away from the surface of the unit cell 12 (peripheral environment) is acquired, the internal temperature of the unit cell 12 is estimated in consideration of heat transfer in the surrounding environment and heat conduction in the unit cell 12. can do. When considering heat transfer and heat conduction, a heat conduction equation or a heat equivalent circuit can be used.

When specifying the internal temperature of the unit cell 12, the internal temperature can be estimated in a model using a heat conduction equation or a heat equivalent circuit. On the other hand, if the calculation load when estimating the internal temperature is reduced, for example, the relationship between the current value of the unit cell 12, the temperature outside the unit cell 12 (environmental temperature), and the internal temperature of the unit cell 12. Is prepared in advance, and the internal temperature can be specified from the current value and the environmental temperature using this map.

As described in the first embodiment, when the current breaker 12b operates in the battery block 11, the value of the current flowing through the single cells 12 included in the battery block 11 increases. Specifically, the current value that flows through the cell 12 after the current breaker 12b is activated is (N / (N−) with respect to the current value that flows through the cell 12 when the current breaker 12b is not activated. m)) is doubled. Here, N is the total number of unit cells 12 constituting the battery block 11, and m is the number of cut-offs. The blocking number m can be specified by the method described in the first embodiment.

Accordingly, when the current breaker 12b is operating, when calculating the temperature rise due to the internal resistance of the unit cell 12, the current value of the unit cell 12 is multiplied by “N / (N−m)”. It is necessary to use a current value. Specifically, a value obtained by multiplying the current value detected by the current sensor 31 by “N / (N−m)” needs to be the current value of the unit cell 12. As a result, the temperature rise can be calculated based on the value of the current actually flowing through the unit cell 12 when the current breaker 12b is operating, and the accuracy of estimating the internal temperature of the unit cell 12 is improved. Can be made. Here, if the value of the current flowing through the single battery 12 is not corrected as described above, the actual internal temperature may become higher than the estimated internal temperature.

When the current breaker 12b is operating in the plurality of battery blocks 11 and the number of interruptions m is different from each other, it is preferable to specify the current value of the unit cell 12 in consideration of the largest interruption number m_max. That is, when calculating the temperature rise due to the internal resistance of the unit cell 12, the current value of the unit cell 12 is set to the current value flowing through the unit cell 12 when the current breaker 12b is not operating. N−m_max) ”can be used. In other words, a value obtained by multiplying the current value detected by the current sensor 31 by “N / (N−m_max)” can be used as the current value of the unit cell 12. Accordingly, the temperature increase (in other words, the internal temperature) can be calculated on the basis of the battery block 11 having the largest number of interruptions m, and the battery block 11 having the largest number of interruptions m can be appropriately protected. .

When the internal temperature of the cell 12 is estimated, charging / discharging of the battery pack 10 (cell 12) can be controlled so that the internal temperature (estimated temperature) of the cell 12 does not become higher than the upper limit temperature.

By controlling charging / discharging of the single cell 12 so that the internal temperature of the single cell 12 does not become higher than the upper limit temperature, it is possible to efficiently suppress the generation of gas in the single cell 12 and protect the single cell 12. can do.

When the internal temperature of the single battery 12 approaches the upper limit temperature, the controller 40 can limit charging / discharging of the assembled battery 10. Specifically, the controller 40 can reduce the upper limit power that allows the battery pack 10 to be charged, or can reduce the upper limit power that allows the battery pack 10 to be discharged. Decreasing the upper limit power includes setting the upper limit power to 0 [kW]. By setting the upper limit power to 0 [kW], the assembled battery 10 is not charged or discharged.

By lowering the upper limit power, charging and discharging of the battery pack 10 are restricted, and the internal temperature of the unit cell 12 can be suppressed from becoming higher than the upper limit temperature.

A battery system that is Embodiment 3 of the present invention will be described. About the member which has the same function as the member demonstrated in Example 1, detailed description is abbreviate | omitted using the same code | symbol. Hereinafter, differences from the first embodiment will be mainly described.

FIG. 9 is a flowchart showing a part of processing in the battery system of the present embodiment. The process shown in FIG. 9 is executed by the controller 40 and performed at a predetermined cycle. The process shown in FIG. 9 can be performed mainly when the vehicle on which the battery system is mounted is an electric vehicle.

In step S201, the controller 40 confirms the operating state of the current breaker 12b in each battery block 11. The method for confirming the operating state of the current breaker 12b is the same as the method described in the first embodiment (step S101 in FIG. 5).

In step S202, the controller 40 determines whether or not the current breaker 12b is operating based on the confirmation result in step S201. That is, the controller 40 determines whether or not the current breaker 12b of any single battery 12 is operating in the assembled battery 10 shown in FIG. 2 or FIG. When any one of the current breakers 12b is operating, the process proceeds to step S203, and when all the current breakers 12b are not operating, the process shown in FIG. 9 is terminated.

In step S <b> 203, the controller 40 specifies the number of current breakers 12 b (the number of interruptions) in the active state in each battery block 11, and sets the largest interruption number m_max among the interruption numbers in all the battery blocks 11. Identify. The method for specifying the number of blocks is the same as the method described in the first embodiment.

In step S204, the controller 40 determines whether or not the cutoff number m_max is equal to or greater than a predetermined number (corresponding to a first threshold) m1. Information about the number m1 can be stored in the memory 41. When the blocking number m_max is greater than or equal to several m1, the process proceeds to step S205, and when the blocking number m_max is smaller than the number m1, the process proceeds to step S206.

In step S205, the controller 40 sets a flag (non-permission flag) that does not allow the battery system to be activated (Ready-On). The setting information of the non-permission flag is stored in the memory 41. When the non-permission flag is set, the controller 40 does not start the battery system even if a signal for starting the battery system is input again after stopping the battery system. Thereby, the controller 40 can prevent the vehicle from running by the output of the assembled battery 10.

Based on the viewpoint of not permitting activation of the battery system, the number m1 used in step S204 can be set as appropriate. Here, as shown in FIG. 10, when the current breaker 12b is activated, the output performance of the assembled battery 10 is degraded. In FIG. 10, the vertical axis indicates the output performance of the assembled battery 10, and the horizontal axis indicates the number of interruptions m_max. Although FIG. 10 shows the output performance of the assembled battery 10, the input performance of the assembled battery 10 is also the same as the output performance, and the input performance decreases as the cutoff number m_max increases.

As shown in FIG. 10, when the number of interruptions m_max is small, the input / output performance of the assembled battery 10 is unlikely to decrease. However, as the number of interruptions m_max increases, the input / output performance of the assembled battery 10 may easily decrease. . In this case, the activation (Ready-On) of the battery system can not be permitted at the shutoff number m_max (= m1) when the rate of decrease in the input / output performance of the assembled battery 10 increases.

The number of interruptions m_max when the input / output performance of the assembled battery 10 reaches the performance required by the vehicle can be specified in advance. The number m1 can be set to a number smaller than the maximum shut-off number m_max that satisfies the required performance of the vehicle. If the number m1 is too smaller than the maximum shut-off number m_max that satisfies the required performance of the vehicle, it is difficult to allow the battery system to be activated. Therefore, the number m1 is preferably set to a number close to the maximum number of shutoffs m_max that satisfies the required performance of the vehicle.

In step S206, the controller 40 determines whether or not the cutoff number m_max is equal to or greater than a predetermined number (corresponding to the second threshold) m2. The number m2 is a number smaller than the number m1 used in step S204, and information regarding the number m2 can be stored in the memory 41. When the cutoff number m_max is greater than or equal to several m2, the process proceeds to step S207, and when the cutoff number m_max is smaller than the number m2, the process proceeds to step S208.

In step S207, the controller 40 issues a warning to the user. The content of the warning may be anything that allows the user to recognize that the battery pack 10 is in an abnormal state. For example, the specific content of the warning includes content for notifying the user that the user is going to the dealer. Sound or display can be used as means for giving a warning. Specifically, the user can be made to recognize the warning by outputting information related to the warning with sound. Further, by displaying information related to the warning on the display, the user can recognize the warning.

The controller 40 performs the process of step S208 after performing the process of step S207. In step S208, the controller 40 specifies the current command value and controls charging / discharging of the assembled battery 10 based on the current command value. The method for specifying the current command value and the method for controlling the charging / discharging of the assembled battery 10 are the same as the method described in the first embodiment (the processes in steps S104 and S105 in FIG. 5).

Even in the process shown in FIG. 9, the current load on the unit cell 12 in which the current breaker 12 b is not operating increases by limiting the value of the current flowing through the assembled battery 10 according to the increase in the number of interruptions m_max. Can be suppressed. Thereby, the same effect as Example 1 can be acquired.

FIG. 11 is a flowchart showing a part of processing in the battery system of the present embodiment. The process shown in FIG. 11 is executed by the controller and performed at a predetermined cycle. The process shown in FIG. 11 can be performed mainly when the vehicle on which the battery system is mounted is a hybrid vehicle. The same processes as those shown in FIG. 9 are denoted by the same reference numerals, and detailed description thereof is omitted. Hereinafter, differences from the processing illustrated in FIG. 9 will be mainly described.

In FIG. 11, in the process of step S204, it is determined whether or not the cutoff number m_max is greater than or equal to several m1. In the present embodiment, the number m1 used in the process of step S204 in FIG. 11 is equal to the number m1 used in the process of step S204 in FIG. 9, but may be different from each other. For example, the number m1 used in the process of step S204 in FIG. 11 can be made larger than the number m1 used in the process of step S204 in FIG. Information about the number m1 can be stored in the memory 41. When the cutoff number m_max is greater than or equal to several m1, the process proceeds to step S210, and when the cutoff number m_max is less than the number m1, the process proceeds to step S206.

Here, when the process proceeds from the process of step S204 to the process of step S210, it is usually after the process of step S206 to step S208 is performed. Therefore, when the process of step S210 is performed, a warning is still given to the user.

In step S210, the controller 40 causes the vehicle to travel without discharging the assembled battery 10. In the hybrid vehicle, in addition to the assembled battery 10, a power source for running the vehicle is provided. Examples of the power source include an engine and a fuel cell. Therefore, in step S210, the controller 40 can drive the vehicle by operating a power source different from that of the assembled battery 10.

Claims

A power storage device including a plurality of power storage elements connected in parallel;
A controller for controlling charging and discharging of the power storage device,
Each of the electricity storage elements has a current breaker that interrupts a current path inside the electricity storage element,
The controller controls charging / discharging of the power storage device based on a current value flowing through the power storage element that is not interrupted by the current path, which changes as the number of the current breakers in the interrupted state increases. A power storage system characterized by that.
The power storage device has a plurality of power storage blocks connected in series,
The power storage system according to claim 1, wherein each power storage block includes the plurality of power storage elements connected in parallel.
3. The controller according to claim 2, wherein the controller uses the largest number among the number of the current breakers in the cut-off state in each power storage block as the number of the current breakers in the cut-off state. Power storage system.
The power storage system according to claim 1, wherein the power storage device includes a power storage element connected in series with each of the power storage elements connected in parallel.
The power storage according to any one of claims 1 to 4, wherein the controller decreases a value of a current flowing through the power storage device in accordance with an increase in the number of the current breakers in a cut-off state. system.
The controller is
Using the amount of temperature change based on the reference current value, estimate the temperature inside the power storage element,
5. The power storage system according to claim 1, wherein charging and discharging of the power storage device is limited as the estimated temperature approaches an upper limit temperature.
The said controller does not permit charging / discharging of the said electrical storage apparatus, when the number of the said current circuit breakers in the interruption | blocking state is more than a 1st threshold value. Power storage system.
The controller issues a warning when the number of the current breakers in a cut-off state is equal to or greater than a second threshold value that is less than the first threshold value and less than the first threshold value. Item 8. The power storage system according to Item 7.
The current breaker is a fuse that cuts off the current path by fusing, a PTC element that cuts off the current path due to an increase in resistance due to a temperature rise, or a deformation in response to an increase in internal pressure of the power storage element, The power storage system according to any one of claims 1 to 8, wherein the power storage system is a current cutoff valve that blocks a current path.